Address feedback about PyList_Reverse

Author: lysnikolaou

Doc/data/threadsafety.dat

@@ -56,9 +56,12 @@ PyList_SET_ITEM:compatible:
 # Bulk operations - hold per-object lock for duration
 PyList_GetSlice:atomic:
 PyList_AsTuple:atomic:
-PyList_Reverse:atomic:
 PyList_Clear:atomic:
 
+# Reverse - protected by per-object critical section; swaps
+# elements so lock-free readers may observe intermediate states
+PyList_Reverse:shared:
+
 # Slice assignment - lock target list; also lock source when it
 # is a list
 PyList_SetSlice:shared: